1. Field of the Invention
The present invention relates generally to a broadband wireless communication system, and in particular, to an apparatus and method for reducing the volume of a resource allocation information message in a broadband wireless communication system.
2. Description of the Related Art
A future-generation communication system called a 4th Generation (4G) system is under an active study to provide services with different Quality of Service (QoS) requirements to users at or above 100 Mbps. An especially active research area concerns provisioning of high-speed services with mobility and QoS ensured to a Broadband Wireless Access (BWA) communication system such as a Wireless Local Area Network (WLAN) and a Wireless Metropolitan Area Network (WMAN). Such a major communication system is an Institute of Electrical and Electronics (IEEE) 802.16e system.
Main standards developed by the IEEE 802.16 working groups are IEEE 802.16d and IEEE 802.16e that are categorized into single carrier, Orthogonal Frequency Division Multiplexing (OFDM), and Orthogonal Frequency Division Multiple Access (OFDMA). The IEEE 802.16d/e OFDMA standard defines DownLink (DL) and UpLink (UL) frame structures with time and frequency resources and radio channel status-based resource allocation in the frames in order to effectively transmit digital bit information to a receiver.
FIG. 1 illustrates a frame structure in a conventional OFDMA communication system.
Referring to FIG. 1, an OFDMA frame includes a DL frame 110 and a UL frame 120.
The DL frame 110 is composed of a preamble 111, a Frame Control Header (FCH) 113, a DL-MAP 115, a UL-MAP 117, and DL data bursts 119.
The preamble 111 provides information by which a Mobile Station (MS) acquires an initial synchronization and performs a cell search. The FCH 113 indicates a coding scheme for the DL-MAP 115 and the UL-MAP 117. The DL-MAP 115 provides a resource allocation information message for each MS and the UL-MAP 117 provides a resource allocation information message for control regions 121 of the UL frame 120 and UL data bursts 123 to be transmitted from MSs. The DL data bursts 119 carry user data from a Base Station (BS) to MSs.
The UL frame 120 is composed of the control regions 121 and the UL data bursts 123. The control regions 121 deliver control information required for communications from the MSs to the BS and the UL data bursts 123 carry user data from the MSs to the BS.
The control regions 121 include a ranging channel 151, a Channel Quality Information (CQI) channel 153, an ACKnowledge (ACK) channel 155, and a sounding channel 157.
An MS can transmit data to the BS without resource allocation from the BS on the ranging channel 151. The ranging channel 151 is used for an initial network entry, a handoff requests, or a resource allocation request. The CQI channel 153 notifies the BS of the DL channel status of the MS. The ACK channel 155 indicates to the BS whether the MS has received a DL data burst successfully. The sounding channel 157 is a region from which the BS acquires channel information about the MS.
In the above-described OFDMA frame structure, the MAP information and the data bursts compete for resources because the MAP regions with the resource allocation information messages and the user data bursts are configured in the same frame. The MAP information and the user bursts are in a trade-off relationship in terms of resources. This means that as the amount of the MAP information increases, the amount of resources are available to the user bursts decreases. Although the frame structure is dynamically variable, the case is rare in real system implementation. Particularly, the control regions 121 of the UL frame 120 tend to have the same configuration in every frame. Transmission of the same resource allocation information message in every frame leads to the decrease of resources available to data bursts, thereby decreasing the overall data rate of the system.